Solution containing flame-resistant polymer and carbon molding

ABSTRACT

A flame-resistant polymer excels in moldability capable of providing a flame-resistant molded item of novel configuration; a relevant flame-resistant polymer solution; a process for easily producing them; a carbon molding from the flame-resistant polymer; and a process for easily producing the same. A flame-resistant polymer is modified with an amine compound. Further, a flame-resistant polymer solution has the polymer dissolved in a polar organic solvent. A flame-resistant molding whose part or entirety is constituted of the flame-resistant polymer modified with an amine compound. A carbon molding was part or entirety constituted of a carbon component resulting from carbonization of the flame-resistant polymer modified with an amine compound. From the solution containing the flame-resistant polymer, moldings of various configurations can be obtained through further work.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.10/590,004, which is published as U.S. Pat. No. 7,655,716 filed Aug. 21,2006, which is a §371 of PCT/JP05/02564, filed Feb. 18, 2005, whichclaims priority of JP 2004-044074 filed Feb. 20, 2004 and JP 2004-265269filed Sep. 13, 2004.

TECHNICAL FIELD

This disclosure relates to a flame-resistant polymer and a solutioncontaining a flame-resistant polymer, and more particularly to aflame-resistant polymer appropriate for obtaining a flame-resistantformed product and the like, a flame-resistant polymer-containingsolution and a manufacturing method thereof.

The disclosure further relates to a flame-resistant formed product, acarbon molded product comprising the above-mentioned flame-resistantpolymer and a manufacturing method thereof.

BACKGROUND

Flame-resistant fiber is so excellent in heat resistance and flameretardance as to be widely utilized, for example, for spatter sheets forprotecting the human body from high-heat iron powder and weld sparkswhich scatter in welding operations, and fire-resistant heat insulatorsfor aircraft, leading to an increasing demand in those fields.

Flame-resistant fiber is important also as intermediate raw materialsfor obtaining carbon fiber. The carbon fiber has such mechanical,chemical properties and lightweight properties as to be widely used forvarious uses, for example, materials for aviation and space such asaircraft, rockets, sporting goods such as tennis rackets, golf shaftsand fishing rods, and in the field of transport machines such as vesselsand automobiles. In recent years, carbon fiber has such a highelectrical conductivity and heat radiation as to be strongly requiredfor application to electronic equipment parts such as portabletelephones and personal computer cabinets, and electrodes of fuel cells.

Carbon fiber is generally obtained by a method of carbonizingflame-resistant fiber by heating at high temperature in an inert gassuch as nitrogen. With regard to flame-resistant fiber, for example,polyacrylonitrile (PAN)-based flame-resistant fiber is obtained bymaking PAN-based precursor fiber flame-resistant (cyclization reactionand oxidation reaction of PAN) at a high temperature of 200 to 300° C.in air.

However, this reaction for making flame-resistant is an exothermicreaction and a reaction in a fibrous form, namely, a solid-phase state.Therefore, a long treatment time is required for temperature control,and the degree of fineness of PAN-based precursor fiber needs to belimited to a fine size below a specific value so that it isflame-resistant within a desired time. Thus, the presently known processof achieving making flame resistance is regarded as difficult and not asufficiently efficient process.

With regard to flame-resistant products, it is substantially difficultto obtain flame-resistant formed products except for fibers, such asplanar shapes of sheets and films and various cubic shapes, due to thedifficulty of heat removal for the reason that the reaction forachieving flame resistance is an exothermic reaction as described above.Accordingly, flame-resistant formed products are limited to fiberformproducts, and in the present circumstances, planar sheets aremanufactured by making such fiberform products into fabrics.

When flame-resistant fiber with an optional degree of fineness andflame-resistant products except fiberform products (flame-resistantformed products), such as sheet-like products and cubic molded productsare obtained, the use of flame-resistant formed products is markedlyextended. In addition, the appropriateness of manufacturing conditionsand carbonizing conditions thereof allows carbon fiber with an optionaldegree of fineness and carbon products except fiberform products (carbonproduct) such as a carbon product group of sheet-like carbon and cubiccarbon molded products. The improvement of yield while maintaining highphysical properties of carbon products brings advantages in costs.

Dissolution by solvents has been studied as a method for solving theabove technical problem.

For example, a technique is disclosed such that acrylonitrile polymerpowder is heated in an inert atmosphere until the density becomes 1.20g/cm³ or more, and thereafter dissolved in solvent and fiberized into afibriform product, which is heat-treated (for example, refer to JapanesePatent Publication No. 63-14093B).

However, the problem is that viscosity change of the solution over timeis so great as to frequently cause thread breakage by reason of usingacrylonitrile polymer powder with low flame resistance. A device made ofspecial materials and having corrosion resistance is to be used withstrongly acidic solvents such as sulfuric acid and nitric acid foreasily decomposing general organic polymers, but is impractical due tocosts.

A method is proposed such that heat-treated acrylonitrile polymer powderand not heat-treated acrylonitrile polymer powder are mixed andsimilarly dissolved in acidic solvent (for example, refer to JapanesePatent Publication No. 62-57723B). However, the problem is still notsolved on allowing corrosion resistance to a device as described aboveand instability of solution.

In addition, the conversion of polyacrylonitrile to a polymer having acyclized chemical structure by heat-treating dimethylformamide solutionof polyacrylonitrile is disclosed (for example, refer to “PolymerScience (USSR),” 1968, Vol. 10, page 1537). However, the polymersolution is a dilute concentration of 0.5% and so low in viscosity as tobe substantially difficult in forming into fibers, and a rise inconcentration thereof causes the polymer to be deposited and incapableof being used as a solution.

On the other hand, a solution in which polyacrylonitrile is denaturedwith a primary amine is disclosed (for example, refer to “Journal ofPolymer Science, Part A: Polymer Chemistry,” 1990, Vol. 28, page 1623).However, the solution is such as to impart a hydrophilic property topolyacrylonitrile itself with low flame resistance, and totally differsin the technical idea from a flame-resistant polymer-containingsolution.

A technique is disclosed such that the yield can be improved togetherwith high physical properties from flame-resistant fiber to carbon fiberunder special carbonizing conditions (for example, refer to JapanesePatent Publication No. 26365093B). However, compatibility therebetweenin an easier method has been demanded.

In view of the above-mentioned problems, it could be helpful to providea flame-resistant polymer so excellent in forming processability as toproduce a flame-resistant formed product also in unprecedented shapes, aflame-resistant polymer-containing solution and a manufacturing methodfor conveniently producing these, and to further provide aflame-resistant formed product, a carbon molded product employing theflame-resistant polymer and a manufacturing method for convenientlyproducing them.

SUMMARY

We thus provide:

(1) a flame-resistant polymer being denatured with an amine compound,

(2) the above-mentioned flame-resistant polymer in which a precursor ofthe flame-resistant polymer is an acrylonitrile polymer,

(3) a flame-resistant polymer-containing solution containing aflame-resistant polymer and a polar organic solvent,

(4) the above-mentioned flame-resistant polymer-containing solution inwhich the polar organic solvent is an amine organic solvent,

(5) the flame-resistant polymer-containing solution according to item(3), in which the amine organic solvent is an amine compound having twoor more functional groups,

(6) the flame-resistant polymer-containing solution according to any oneof the above items, in which the flame-resistant polymer is denaturedwith the amine compound,

(7) the flame-resistant polymer-containing solution according to any oneof the above items, in which the above-mentioned flame-resistant polymeris obtained by using an acrylonitrile polymer as a precursor,

(8) the flame-resistant polymer-containing solution according to any oneof the above items, in which a concentration of the flame-resistantpolymer calculated by the following expression is 2 to 70% by weight;flame-resistant polymer concentration (% by weight)=100× flame-resistantpolymer weight (g)/flame-resistant polymer-containing solution weight(g) where flame-resistant polymer weight indicates a weight of solidcomponent remaining in heating the flame-resistant polymer-containingsolution in nitrogen at a rate of 50° C./minute up to 300° C.,

(9) a method of manufacturing a flame-resistant polymer-containingsolution containing a flame-resistant polymer and a polar organicsolvent, including making a precursor of the flame-resistant polymerflame-resistant in an amine organic solvent or the polar organic solventcontaining an amine compound,

(10) a method of manufacturing a flame-resistant polymer-containingsolution containing a flame-resistant polymer and a polar organicsolvent, including dissolving the flame-resistant polymer in an amineorganic solvent or the polar organic solvent containing an aminecompound,

(11) a flame-resistant formed product comprising a part or the wholethereof composed of a flame-resistant polymer denatured with an aminecompound,

(12) the above-mentioned flame-resistant formed product being fibrous,

(13) the flame-resistant formed product according to item (11), being asheet and having a thickness of 5 mm or less,

(14) a carbon molded product comprising a part or the whole thereofcomposed of a carbon component obtained by carbonizing a flame-resistantpolymer denatured with an amine compound,

(15) the above-mentioned carbon molded product being fibrous,

(16) the carbon molded product according to item (14), being a sheet andhaving a thickness of 5 mm or less,

(17) the carbon molded product according to any one of items 14 to 16,in which a crystal size Lc (angstroms) measured by wide-angle X-rays is30 or less, and Lc and a nitrogen content N (% by weight) satisfy[N≧0.04(Lc−30)^2+0.5],

(18) a method of manufacturing a flame-resistant formed productcomprising the steps of:

forming the flame-resistant polymer-containing solution according to anyone of items (3) to (8); and removing a solvent after theabove-mentioned step,

(19) the above-mentioned method of manufacturing a flame-resistantformed product, in which the above-mentioned step of forming is the stepof forming into being a sheet,

(20) the method of manufacturing a flame-resistant formed productaccording to item (18), in which the above-mentioned step of forming isthe step of forming into being fibrous,

(21) a method of manufacturing a carbon molded product, characterized bycarbonizing the flame-resistant formed product according to any one ofitems (11) to (13), and (22) a method of manufacturing a carbon moldedproduct, including carbonizing a flame-resistant formed product obtainedby the method according to any one of items (18) to (20).

We provide solutions containing a flame-resistant polymer which can beformed into various shapes as described below. The use of such aflame-resistant polymer results in a flame-resistant formed product alsoin unprecedented shapes. Such a flame-resistant molded product candirectly be carbonized and carbon products in various shapes canefficiently be manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual view of a dry spinning method used in Example 2.

FIG. 2 is a solid NMR spectrum of a flame-resistant polymer denaturedwith amine obtained in Example 6 and flame-resistant fiber not denaturedwith amine obtained in Example 5.

REFERENCE NUMERALS

Reference numerals are as follows.

-   -   1 flame-resistant polymer flow path    -   2 spinning head    -   3 spinning cylinder    -   4 heated nitrogen inlet    -   5 heated nitrogen outlet    -   6 fibrous flame-resistant formed product    -   7 wind-up roller

DETAILED DESCRIPTION

A flame-resistant polymer is a polymer having flame resistance and aflame-resistant polymer-containing solution is a solution in which acomponent mainly including a flame-resistant polymer is dissolved in anorganic solvent. The solution is preferred to be viscous fluid and asolution having flowability in forming and molding, and includessolutions having flowability at room temperature as well as allsolutions having flowability around processing temperature by heatingand shear force even though solids and gels have no flowability at sometemperature.

Flame resistance signifies substantially the same as the term ‘fireresistance’ and includes the term ‘flame retardance’. Specifically,flame resistance is a general term denoting properties of difficulty tocontinue combustion, namely, difficulty in burning. A fire resistancetest method of thin materials (45° Meckel burner method) is described asa specific means of evaluating flame-resistant performance, for example,in JIS Z 2150 (1966). A test sample to be evaluated (board, plate,sheet, film, thick fabric and the like having a thickness of less than 5mm) can be determined by heating with a burner for a specific time toevaluate flaming time, carbonized length etc. after igniting. Shorterflaming time and shorter carbonized length are determined as excellentflame-resistant (fire-resistant) performance. In the case of fiberproducts, a combustion test method of fiber is described in JIS L 1091(1977). Fiber products can similarly be determined by measuringcarbonized area and flame time after testing by the method. Shapes andforms of flame-resistant polymers and flame-resistant formed productsare of such various kinds as to cover a wide range in the degree offlame-resistant performance from very high flame resistance exhibitingno ignition at all to a certain continuation of combustion afterignition, and flame-resistant polymers and flame-resistant formedproducts which offer flame-resistant performance on a predeterminedlevel or higher by a specific evaluation method described in theafter-mentioned examples. Specifically, flame-resistant performance ispreferably ‘excellent’ or ‘favorable’. In particular, at the stage offlame-resistant polymers, the conditions of isolation cause shapes andforms of the polymers to change and flame resistance to easily varygreatly, so that it is preferable to adopt a method of evaluating afterforming into predetermined shapes.

Flame-resistant formed products such as flame-resistant fibers formedout of flame-resistant polymers can also be measured by a specific meansof evaluating flame resistance described in the after-mentionedexamples.

Flame-resistant polymers are typically the same or similar to chemicalstructure of the so-called “flame-resistant” fiber and stabilized fiber,and examples thereof include polyacrylonitrile polymer heated in air asa precursor, oxidized pitch raw material on the basis of petroleum andcoal, and phenolic resin precursor. Flame-resistant polymers obtained byusing polyacrylonitrile as a precursor are preferable in view of easydissolution.

In the case of using polyacrylonitrile polymer as a precursor, thestructure of flame-resistant polymer is not completely definite andconceived to have a structure of naphthyridine ring, acridone ring orhydrogenated naphthyridine ring caused by cyclization reaction oroxidation reaction of nitrile groups as recited in the Journal ofPolymer Science, Part A: Polymer Chemistry Edition, 1986, Vol. 24, page3101, which flame-resistant polymer is generally called “ladder” polymerin view of its structure. Needless to say, it is no problem unless flameresistance is deteriorated even though unreacted nitrile groups remain,and no problem unless solubility is deteriorated even though crosslinkage is caused in a very small quantity between molecules.

In the case of measuring 13-C of the flame-resistant polymer itself orsolution thereof by a nuclear magnetic resonance (NMR) apparatus, astructure having signals in 150 to 200 ppm resulting from the polymer ispreferable. Absorption in that range renders flame resistance favorable.

The molecular weight of flame-resistant polymer is not particularlylimited, but is preferred to be a molecular weight having viscosityaccording to forming methods.

A flame-resistant polymer denatured with an amine compound is preferablyused as a flame-resistant polymer. Examples of the state ‘denatured withan amine compound’ herein include a state such that an amine compound ischemically reacted with a raw material precursor polymer, or a statesuch that an amine compound is taken into the polymer by interactionsuch as hydrogen bonds or van der Waals forces. It is found by thefollowing method whether a flame-resistant polymer in a flame-resistantpolymer-containing solution is denatured with an amine compound.

A. Spectroscopic method, such as a means of analyzing the difference instructure from undenatured polymer by using the above-mentioned NMRspectrum, infrared absorption (IR) spectrum and the like.

B. Means of confirming by measuring flame-resistant polymer weight in aflame-resistant polymer-containing solution by the after-mentionedmethod to confirm whether the weight increases with respect to aprecursor polymer as raw materials.

In the case of the former means, a part derived from an amine compoundand used as a denaturant is added to a flame-resistant polymer denaturedwith an amine compound with respect to a polymer typically obtained byair oxidation (not denatured with an amine compound).

In the case of the latter means, typically, the same weight as theweight of the precursor fiber is generally obtained in theflame-resistant fiber by air oxidation, and the weight is increased bydenaturing with amine by 1.1 times or more, 1.2 times or more and 1.3times or more in increasing order of preference with respect to theprecursor polymer. The amount of increase is 3 times or less, 2.6 timesor less and 2.2 times or less at the upper limit in increasing order ofpreference. A small change in weight brings a tendency to renderdissolution of a flame-resistant polymer insufficient, and creates thepossibility that the polymer component becomes “foreign matter” inmaking flame-resistant formed products and carbon molded products. Onthe other hand, a great change in weight occasionally deteriorates flameresistance of the polymer.

A flame-resistant polymer can be water-insoluble or water-soluble.Water-insolubility or water-solubility is related to selection ofsolvents and rate of the above-mentioned change in weight, and higherweight increase rate in using an amine compound as a solvent isrecognized to bring a tendency to be water-soluble; however, the detailsare not apparent.

Water-insoluble or water-soluble polymer can properly be selected byobjects and uses, and more heat treatment leads to water-insolublepolymer more frequently at the later stage of formed products.

An amine compound capable of being used for amine denaturation to obtaina flame-resistant polymer may be any compounds having primary toquaternary amino groups. Specific examples thereof include ethanolaminessuch as monoethanolamine, diethanolamine, triethanolamine andN-aminoethyl ethanolamine, polyethylene polyamines such asethylenediamine, diethylenetriamine, triethylenetetramine,tetraethylenepentamine, pentaethylenehexamine and N-aminoethylpiperazine, and ortho-, meta- and para-phenylenediamines.

In particular, the compounds preferably have functional groups havingelements such as oxygen, nitrogen and sulfur, for example, hydroxylgroups besides amino groups, and compounds having two or more functionalgroups including amino groups and functional groups except such aminesare preferable from the viewpoint of reactivity. These can be used inone kind, or two kinds or more together. In the case of compounds havingfunctional groups except amino groups, such as hydroxyl groups, hydroxylgroups can denature a flame-resistant polymer.

A flame-resistant polymer can be made into a solution using an organicsolvent as solvent. The content of a flame-resistant polymer is 2% byweight or mole, 10% by weight or more and 20% by weight or more at thelower limit in increasing order of preference, and 70% by weight orless, 60% by weight or less and 50% by weight or less at the upper limitin increasing order of preference. In the case of low concentration, theeffect itself is not deteriorated and productivity in molding isoccasionally low. In the case of high concentration, flowability is sopoor as to occasionally perform molding process with difficulty.Flame-resistant polymer concentration is calculated by the followingexpression: flame-resistant polymer concentration (% byweight)]=100×[flame-resistant polymer weight]/[flame-resistantpolymer-containing solution weight]. Flame-resistant polymer weight iscalculated by using a thermogravimetric analysis instrument (TG) asweight of solid component remaining in heating flame-resistantpolymer-containing solution in nitrogen gas at a rate of 50° C./minuteup to 300° C. In the case where the use of proper coagulant(precipitant) allows solid polymer to be separated, flame-resistantpolymer weight can directly be calculated from the weight of coagulativepolymer. Specifically, in the case of water-insoluble polymer,flame-resistant polymer-containing solution is projected into water tosufficiently wash water-soluble component out of the polymer with warmwater of 90° C. and calculate flame-resistant polymer weight as theweight of solid polymer after drying.

An amine organic solvent can be used as an organic solvent. Such asolvent may be any compounds having primary to quaternary aminestructure. The use of such an amine organic solvent allows aflame-resistant polymer-containing solution, in which a flame-resistantpolymer is uniformly dissolved, and a flame-resistant polymer havingfavorable moldability together.

A flame-resistant polymer can also be made into a solution using a polarorganic solvent as the solvent. This solvent can contain an aminecompound such as an amine organic solvent. The reason is that aflame-resistant polymer denatured with an amine compound has such a highpolarity that a polar organic solvent dissolves the polymer well.

A polar organic solvent has hydroxyl groups, amino groups, amide groups,sulfonyl groups, sulfone groups and the like, and additionally favorablecompatibility with water. Specific examples thereof include ethyleneglycol, diethylene glycol, triethylene glycol, polyethylene glycolhaving a molecular weight of approximately 200 to 1000, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone,the above described as amine organic solvents, namely, ethanolaminessuch as monoethanolamine, diethanolamine, triethanolamine andN-aminoethyl ethanolamine, polyethylene polyamines such asethylenediamine, diethylenetriamine, triethylenetetramine,tetraethylenepentamine, pentaethylenehexamine and N-aminoethylpiperazine, and ortho-, meta- and para-phenylenediamines, which can beused also as an amine denaturant. These may be used in only one kind, ora mixture of two kinds or more.

Above all, dimethyl sulfoxide is preferable in view of being applicableto wet spinning for the reason that a flame-resistant polymer is soeasily coagulated in water as to easily become a minute and hardpolymer.

In the case of an amine solvent, the solvent preferably has functionalgroups having elements such as oxygen, nitrogen and sulfur, for example,hydroxyl groups besides amino groups, and compounds having two or morefunctional groups including amino groups and functional groups exceptsuch amines are preferable from the viewpoint of solubility. Aflame-resistant polymer-containing solution, in which a flame-resistantpolymer is more uniformly dissolved, allows flame-resistant formedproducts with less foreign matter, and allows the after-mentionedmoldability into being fibers and sheets to be improved.

Within a range of not impairing characteristics, for example, awater-soluble flame-resistant polymer may be made into a uniformsolution by using other solvents such as water (for example,water-soluble solvents) in combination with a polar organic solvent. Theuse of water is preferable from the viewpoint of the after-mentionedcomparative easiness of removing solvents during molding as well ascosts. The added amount of water is 5 parts by weight or more, 10 partsby weight or more and 20 parts by weight or more at the lower limit, and300 parts by weight or less, 200 parts by weight or less and 150 partsby weight or less at the upper limit in increasing order of preferencewith respect to 100 parts by weight of a flame-resistant polymer.

In the case of an amine solvent, polar organic solvents such as ethyleneglycol, diethylene glycol, triethylene glycol, polyethylene glycolhaving a molecular weight of approximately 200 to 1000, dimethylsulfoxide, dimethylformamide, dimethylacetamide and N-methylpyrrolidonemay be contained as a small amount of other components to be mixed. Theuse of such compounds together with an amine organic solvent ispreferable by reason of not merely allowing a flame-resistantpolymer-containing solution at low costs but also facilitating theafter-mentioned removal of solvents in the step of molding.

The viscosity of a flame-resistant polymer-containing solution can bedetermined at a preferable range by each of forming methods and moldingmethods using polymer, molding temperature, and kinds of mouthpieces andmetal molds. The viscosity can generally be used at a range of 1 to100000 Pa·s at a temperature of 50° C.; preferably 10 to 10000 Pa·s,more preferably 20 to 1000 Pa·s. Such viscosity can be measured byvarious kinds of viscometers such as rotary viscometer, rheometer andB-type viscometer. The viscosity is preferred to be determined in theabove-mentioned range by any measuring method. Even though the viscosityis out of such a range, the viscosity can be made into a properviscosity by heating or cooling during forming.

Next, examples of a method of manufacturing a flame-resistantpolymer-containing solution are described. Examples of a method ofobtaining a flame-resistant polymer-containing solution include thefollowing methods:

A. Method of making a precursor polymer flame-resistant in a solution;and

B. Method of directly dissolving a flame-resistant polymer component ina solvent.

In any of the above-mentioned methods, examples of a precursor polymeras raw materials include polyacrylonitrile polymer, polymer using pitchmade of petroleum and coal as raw materials, and phenolic resin. Aboveall, polyacrylonitrile polymer is preferable in view of solubility.

Polyacrylonitrile polymer preferably comprises acrylic polymer having astructure derived from acrylonitrile in view of easy progression of thereaction to achieve flame resistance and solubility. In the case of suchacrylic copolymer, the structural unit derived from acrylonitrilepreferably comprises copolymer preferably comprising 85 mol % or more,more preferably 90 mol % or more and further more preferably 92 mol % ormore of acrylonitrile and other copolymer components. The method ofpolymerizing such acrylonitrile polymer is not particularly limited. Thesolution polymerization method, suspension polymerization method, slurrypolymerization method and emulsion polymerization method are applicable.

Specific examples of copolymer components include allyl sulfonic acidmetallic salt, methacryl sulfonic acid metallic salt, acrylate ester,methacrylate ester and acrylamide. Compounds containing vinyl groups,specifically acrylic acid, methacrylic acid and itaconic acid, can becopolymerized as components for promoting to make flame-resistantbesides the above-mentioned copolymer components, and partial or thewhole amount of the compounds may be neutralized with alkalinecomponents such as ammonia. The number-average molecular weight ofacrylonitrile polymer can optionally be selected from approximately 1000to 1000000. The number-average molecular weight can be calculated frommeasurement of intrinsic viscosity of dilute solution.

In the case of dissolving a precursor polymer in a polar organicsolvent, shapes and forms of the precursor polymer may be any of powder,flake and fiber, and polymer waste and yarn waste caused duringpolymerization and spinning can also be used as recycling raw materials.The state of powder, particularly, particulates of 100 μm or less ispreferable in view of solubility in the solvent. The precursor polymeris previously dissolved in the solvent at the stage of a monomer andpolymerized by a polymerization method to obtain a polymer solution,which can also directly be used.

In the case of directly dissolving a flame-resistant polymer in a polarorganic solvent, a polymer can be used such that the above-mentionedprecursor polymer is oxidized under an oxygen atmosphere at a desiredtemperature, for example, 200 to 300° C. With regard to such a polymerwith flame resistance promoted, shapes thereof are not particularlylimited but may be fibrous, particulate, powdery or porous. Aflame-resistant polymer may be used such that a precursor polymerpreviously made into the above-mentioned shapes is made flame-resistant,and a precursor polymer like a filament yarn may be madeflame-resistant, and thereafter cut and processed into desired shapes.Commercial flame-resistant products may be used, and waste caused in thesteps of manufacturing such flame-resistant products may be used. Suchmethods allow once caused flame-resistant fiber waste to be recycled andmanufactured for flame-resistant products.

Even in the case of dissolving a precursor polymer in an amine solventor a polar organic solvent in the presence of an amine compound, andeven in the case of dissolving a flame-resistant polymer in an aminesolvent or a polar organic solvent in the presence of an amine compound,the dissolution may be performed under normal pressure, or underpressurization or decompression depending on the situation. Mixers suchas extruders and kneaders except ordinary reaction vessels with astirrer can be used singly or in combination as apparatuses used fordissolving.

In this case, the dissolution is preferably performed by using 100 to1900 parts by weight, more preferably 150 to 1500 parts by weight of anamine solvent or the total of an amine compound and a polar organicsolvent with respect to 100 parts by weight of an acrylonitrile polymer.

In the case where a precursor polymer is dissolved in an amine solventor a polar organic solvent in the presence of an amine compound andthereafter made flame-resistant, oxidizing agents are preferably used tosufficiently promote flame resistance. Oxidizing agents can be used forfurther improving the degree of flame resistance. Examples of suchoxidizing agents to be used include organic or inorganic oxidizingagents. Above all, it is preferable to add air in view of handling andcosts. Oxidizing agents to be easily mixed into solvent systems arepreferably used for uniformly promoting flame resistance or dissolved ina liquid phase. Specific examples thereof include nitro, nitroxide andchinone-based oxidizing agents. Above all, particularly preferableexamples thereof include aromatic nitro compounds such as nitrobenzene,ortho-, meta- and para-nitrotoluene, and nitroxylene. The added amountof these oxidizing agents is not particularly limited, and preferably0.01 to 100 parts by weight, more preferably 1 to 80 parts by weight andfurther more preferably 3 to 60 parts by weight with respect to 100parts by weight of a precursor polymer. Such compounding ratiofacilitates the control of concentration of a flame-resistantpolymer-containing solution finally obtained in the above-mentionedpreferable range.

In the case where a precursor polymer is dissolved in an amine solventor a polar organic solvent in the presence of an amine compound andthereafter made flame-resistant, an amine solvent and oxidizing agents,or an amine compound and a polar organic solvent and oxidizing agentsmay be mixed before adding a precursor polymer or mixed simultaneouslywith a precursor polymer. It is preferable in view of less insolublematter that a precursor polymer, an amine compound and a polar organicsolvent are previously mixed and dissolved by heating, to whichoxidizing agents are then added to obtain a flame-resistant polymer.Needless to say, components except a precursor polymer, oxidizingagents, an amine compound and a polar organic solvent are not preventedfrom being mixed into such a solution.

Such a mixed solution of a precursor polymer, an amine compound and apolar organic solvent is heated at proper temperatures to therebypromote dissolution of the precursor polymer or flame resistance. Onthis occasion, temperatures vary with solvents and oxidizing agents tobe used, being preferably 100 to 350° C., more preferably 110 to 300° C.and further more preferably 120 to 250° C. Needless to say, even in thecase of dissolving a precursor polymer with flame resistance previouslyperformed, heating may further promote flame resistance.

A flame-resistant polymer-containing solution obtained by theabove-mentioned method preferably includes no unreacted matter,insoluble matter and gel, which can remain in very small quantities.Depending on the cases, unreacted matter and insoluble matter arepreferably filtered and dispersed by using a sintered filter or the likebefore molding into fiber.

A flame-resistant polymer-containing solution may include inorganicparticles such as silica, alumina and zeolite, pigment such as carbonblack, antifoaming agent such as silicone, stabilizer and flameretardant such as phosphorus compounds, various kinds of surfactants,and other addition agents. Inorganic compounds such as lithium chlorideand calcium chloride can be included for the purpose of improvingsolubility of the flame-resistant polymer. These may be added beforepromoting flame resistance or after promoting flame resistance.

In the case where ethylene glycol, diethylene glycol, triethyleneglycol, polyethylene glycol, dimethyl sulfoxide, dimethylformamide,dimethylacetamide as the above-mentioned polar compounds are included,these compounds may be added to an amine organic solvent or included ina precursor polymer.

Viscosity, polymer concentration, the degree of flame resistance andkinds of solvents of a flame-resistant polymer-containing solutionfinally obtained can be adjusted to the above-mentioned preferablerange.

Next, flame-resistant formed products employing a flame-resistantpolymer are described. Flame-resistant formed products are such that apart or the whole thereof is composed of a flame-resistant polymerdenatured with an amine compound. Flame-resistant formed products may becomposed of the above-mentioned flame-resistant polymer-containingsolution compounded into other polymers and compounds.

Such flame-resistant formed products can be obtained through the step offorming the above-mentioned flame-resistant polymer-containing solutionand the step of removing a solvent.

Such flame-resistant products may be fibrous, sheet, other cubic orplanar shapes. That is, forming into fibers in the step of formingallows fibrous flame-resistant formed products, the forming into sheetsallows sheet flame-resistant formed products, and the forming into othercubic shapes allows cubic flame-resistant formed products.

Fibrous flame-resistant formed products may be like a filament yarn orstaple fiber. In the case of being like a filament yarn, theflame-resistant formed products are parallel and used directly as rawmaterials of carbon fibers, while in the case of being like staplefibers, the flame-resistant formed products made into a fabric such astextile, knitted goods and nonwoven fabric by using crimped fibers asthe material.

Fibrous flame-resistant formed products may be a single fiber or fiberstrand made of plural single fibers. In the case of being made into afiber strand, the number of single fibers in a strand is determined bypurpose of use, being preferably 50 to 100000 pieces/strand, morepreferably 100 to 80000 pieces/strand and further more preferably 200 to60000 pieces/strand in view of high-order processability.

The degree of fineness of each single fiber is preferably 0.00001 to 100dtex, more preferably 0.01 to 100 dtex in the case of being used as rawmaterials of carbon fiber, and meanwhile preferably 0.1 to 100 dtex,more preferably 0.3 to 50 dtex in the case of being processed intofabric. The diameter of single fiber is preferably 1 nm to 100 μm, morepreferably 10 nm to 50 μm in the case of being used as raw materials ofcarbon fiber, and meanwhile preferably 5 to 100 μm, more preferably 7 to50 μm in the case of being processed into fabric.

The cross-sectional shape of each single fiber of fibrousflame-resistant formed products may be circular, elliptical, cocoon typeor an indefinite shape depending on the situation.

The specific gravity of fibrous flame-resistant formed products ispreferably 1.1 to 1.6, more preferably 1.15 to 1.55 and further morepreferably 1.2 to 1.5. A specific gravity of less than 1.1 occasionallybrings so many holes as to decrease strength, while a specific gravityof more than 1.6 occasionally brings so high a denseness as to decreaseductility. The specific gravity can be measured by immersion method andsink-float method.

The single fiber tensile strength of fibrous flame-resistant formedproducts is preferably 0.1 to 10 g/dtex, more preferably 0.2 to 9 g/dtexand further more preferably 0.3 to 8 g/dtex. Such tensile strength canbe measured by using a universal tensile tester (such as Model 1125,manufactured by Instron Corporation) in conformity to JIS L1015 (1981).

The residual amount of solvent components contained in fibrousflame-resistant formed products is preferably 10% by weight or less,more preferably 5% by weight or less and further more preferably 1% byweight or less. Such a solvent residual rate of more than 10% by weightoccasionally deteriorates flame resistance.

Next, a method of manufacturing flame-resistant formed products isdescribed. With regard to flame-resistant formed products, theabove-mentioned flame-resistant polymer-containing solution can directlybe processed into flame-resistant formed products in fibrous, sheetlike,other planar or cubic shapes. Depending on the situation, aflame-resistant polymer can be compounded into other polymers andcompounds, and formed and molded to obtain flame-resistant formedproducts. Specifically, a flame-resistant polymer-containing solutioncan be compounded into an acrylonitrile polymer and thereafter spun toobtain fibrous flame-resistant formed products, or the flame-resistantpolymer-containing solution can be compounded into epoxy resin andthereafter molded and cured to obtain flame-resistant formed products.In this case, a polar organic solvent, particularly preferably an amineorganic solvent, can also directly be utilized as a curing agent ofepoxy resin. The solvent can be used for extensive uses by reason ofbeing dissolved.

Next, with regard to each of flame-resistant formed products in fibrous,sheet or other shapes, a specific method of manufacturing is describedbelow.

A method of molding a flame-resistant polymer-containing solution intobeing fibrous, namely, obtaining flame-resistant fibers is notparticularly limited, and spinning methods such as wet spinning method,semi-dry spinning method, dry spinning method and flash spinning methodcan be applied directly or through improvement. Electronic spinningmethod can also be used.

Dry spinning method is preferable in view of convenience of theprocesses, and a method of discharging a flame-resistant polymer from amouthpiece to vaporize the solvent. Depending on the situation, it canbe used together so that coagulation is promoted in a water bathaccommodating metallic salt to remove water-soluble components. A dryingmethod such as blowing ordinary hot air and steam, irradiating withinfrared rays and high-frequency electromagnetic waves, and reducingpressure can be selected. Ordinary hot air can be blown in a parallelflow or cross flow in the traveling direction of fiber. Far infraredrays, mid-infrared rays and near infrared rays can be used for infraredrays of the radiation heating type, and irradiation of microwaves canalso be selected. Drying temperature can optionally be determined in arange of approximately 50 to 450° C.

Wet spinning and semi-dry spinning methods are preferable for improvingproductivity of the processes, and water can be used as one component ofa coagulation bath by selecting a water-insoluble flame-resistantpolymer. Specifically, coagulation is performed in a water bath or amixing bath of solvent/water at approximately 10 to 60° C., andcoagulated yarn is washed and drawn or contracted to remove solvents inthe yarn and thereafter dry in a range of approximately 50 to 450° C.The same method as dry spinning method can be selected as the dryingmethod. In addition, heat treatment can also be performed in a range ofapproximately 200 to 400° C. Coagulation bath concentration can bedetermined in an optional range of solvent/water=0/100 to 95/5.Coagulation bath temperature can be determined at an optionaltemperature of 0 to 100° C. With regard to a coagulation bath, alcoholshaving reduced affinity with water such as propanol and butanol can beused for 100%-bath.

Either of filament yarns and staple fibers can be obtained asflame-resistant fiber. Either method of cold drawing and hot drawing canbe used for further drawing. Hot air and steam are properly selected forheating. The draw ratio is preferably 1.1 to 4 times, more preferably1.2 to 3 times and particularly preferably 1.3 to 2 times. The drawratio is determined by strength and degree of fineness of theflame-resistant fiber to be required.

Lubricants are added in accordance with necessity of high-orderprocessing. The kinds of lubricants are not particularly limited, andpolyether and polyester surfactants, silicone, amino-denatured silicone,epoxy-denatured silicone and polyether-denatured silicone are addedsingly or in a mixture, and other lubricants may be added.

Fibrous formed products may be strands made of plural single fibers, andthe number of single fibers included in a strand is selected for purposeof use. The above-mentioned preferable number thereof can be obtained byadjustment of mouthpiece hole number or doubling of fibrousflame-resistant formed products of plural pieces.

The degree of fineness of single fibers can be controlled to theabove-mentioned preferable range by selecting the diameter of mouthpiecehole and determining the discharge amount from mouthpiece.

In the case of increasing the degree of fineness of a single fiber, itis preferable in view of decreasing the solvent residual amount toprolong the drying time or raise the drying temperature. In the case ofobtaining fibrous flame-resistant formed products having a lower degreeof fineness of a single fiber, an electronic spinning method ispreferably used. Such a method also allows the degree of fineness on ananofiber level; preferably a diameter of 100 nm or less, morepreferably 1 to 100 nm and further more preferably 5 to 50 nm.

The cross-sectional shape of fibrous flame-resistant formed products(flame-resistant fiber) can be controlled by shapes of circular holes,elliptical holes and mouthpiece discharge holes such as slits, andconditions of removing solvent.

The specific gravity of flame-resistant fibers can be controlled, forexample, by drying or heat-treating conditions. The specific gravity inthe above-mentioned preferable range can be obtained by setting a dryingtemperature of 50 to 450° C. as drying conditions and a range of 200 to400° C. as heat-treating conditions. Drying in air promotes oxidationand occasionally leads to a preferable phenomenon such as an increase incarbonization yield.

A higher drying temperature than the boiling point of the solvent asdrying conditions allows residual amount of solvent and volatilecomponent in flame-resistant fiber to be set at 10% or less as describedabove.

Next, sheetlike flame-resistant formed products are described.‘Sheetlike’ herein is a concept also including thin films. The thicknessis not particularly limited; preferably 5 mm or less, more preferably 2mm or less and further more preferably 1 mm or less. A thickness of morethan 5 mm has a tendency to be brittle. A preferable thickness can beselected in accordance with use, and a thickness as thin asapproximately 0.5 mm is frequently enough to use as general industrialproducts.

A preferable range of specific gravity of sheetlike flame-resistantformed products is 1.1 to 1.6. A specific gravity of less than 1.1occasionally causes cracks, while a specific gravity of more than 1.6occasionally brings low ductility.

A preferable range of volatile component content of sheetlikeflame-resistant formed products is 10% by weight or less. A volatilecomponent content of more than 10% by weight occasionally deterioratesflame resistance. Less volatile component content is more preferred,more preferably 5% by weight or less, further more preferably 3% byweight or less and ideally 0; a content of approximately 1% by weightoccasionally causes no practical problems.

Next, examples of manufacturing methods of sheetlike flame-resistantformed products are described. Examples thereof include a method ofmaking the above-mentioned flame-resistant polymer-containing solutioninto a sheetlike form by a cast film forming method. The solution isuniformly cast and thereafter dried in a constant-temperature dryer, andalso gelatined in a bath such as water bath depending on the cases. Theform can directly be fixed in a coagulation bath.

Flame-resistant formed products can be made into being theabove-mentioned fibrous, sheetlike, planar or cubic shapes of variouskinds, for example, particulate typified by globes, tabular typified bythin sheets, columnar typified by sticks and indefinite shapes.

Examples of manufacturing methods of such products are described.Molding methods used in thermoplastic resin and thermosetting resin canbe used. For example, injection molding, extrusion molding andcompression molding. Cast molding method can also be applied thereto.Cast molding is preferable in view of allowing diverse shapes.Specifically, the above-mentioned flame-resistant polymer-containingsolution is put into a die in favorite shapes and dried to some degreein a constant-temperature dryer, for example. In addition, the solutionis fixed in final shapes by using an embossing die immediately beforenot fluidizing. In this case, a flame-resistant polymer-containingsolution to be used is not particularly limited if it is describedabove, and a flame-resistant polymer concentration of 5 to 50% by weightis preferably used in view of flowability. A viscosity of 10 to 150 Pa·sat a temperature of 50° C. is preferable in view of flowability.

Carbon molded products can be obtained by further carbonizing theabove-mentioned flame-resistant molded products of various kinds. Carbonmolded products include fibrous carbon molded products (carbon fiber),sheetlike carbon products (carbon sheet) and carbon molded products inother shapes. ‘Carbon molded products’ herein has a carbon content of80% by weight or more, more preferably 90% by weight or more.

In addition, with regard to carbon molded products, it is preferablethat a crystal size Lc (angstroms) measured by wide-angle X-rays is 30or less, and a nitrogen content N (% by weight) satisfyN≧0.04(Lc−30)^2+0.5. The range is preferable in view of costs for thereason that a high nitrogen amount improves the yield of carbon moldedproducts while high crystallinity maintains good physical properties.The nitrogen content can be measured by using an elemental analyzer.Generally, the increase of a crystal size of carbon molded productsdecreases the nitrogen content due to pyrolysis. However, carbon moldedproducts in this range can easily be formed by carbonizingflame-resistant formed products, which use a flame-resistant polymerdenatured with amine as materials.

With regard to fibrous carbon products, strength is 100 MPa or more, 200MPa or more and 300 MPa or more at the lower limit, and 10000 MPa orless, 8000 MPa or less and 6000 MPa or less at the upper limit inincreasing order of preference. When the strength is low, the productcannot be used as a reinforced fiber. Higher strength is more preferred,and 1000 MPa is occasionally sufficient depending on the objective.

With regard to fibrous carbon products, fiber diameter is preferably 1to 7×10⁴ nm, more preferably 10 to 5×10⁴ nm and further more preferably50 to 10⁴ nm. A fiber diameter of less than 1 nm results in the fiberbeing easily broken, while a fiber diameter of more than 7×10⁴ nm has atendency to easily cause defects. With regard to fibrous carbonproducts, the specific gravity is preferably 1.3 to 2.4, more preferably1.6 to 2.1 and particularly preferably 1.6 to 1.75. A specific gravityof less than 1.3 causes the fiber to be easily broken, while a specificgravity of more than 2.4 has a tendency to easily cause defects.Specific gravity can be measured by liquid immersion method andsink-float method. Fibrous carbon products may be hollow carbon fiberincluding a hollow part. In this case, the hollow part may be continuousor discontinuous.

A specific method of obtaining fibrous carbon products treats theabove-mentioned fibrous flame-resistant formed products (flame-resistantfiber) in an inert atmosphere at a maximum temperature in a range of300° C. or more and less than 2000° C. The maximum temperature is 800°C. or more, 1000° C. or more and 1200° C. or more at the lower limit inincreasing order of preference, and usably 1800° C. or less at the upperlimit.

Such carbon fiber can also be made into graphite fiber by furtherheating in an inert atmosphere at a temperature of 2000 to 3000° C.

The obtained carbon fiber and graphite fiber can be electrolyticallytreated for surface modification thereof. Examples of electrolyticsolution used for electrolytic treatment include acid solutions such assulfuric acid, nitric acid and hydrochloric acid, and aqueous solutionsof alkalis such as sodium hydroxide, potassium hydroxide andtetraethylammonium hydroxide, or salts thereof. Electrical quantityrequired for electrolytic treatment can properly be selected by carbonfiber and graphite fiber to be applied.

Such electrolytic treatment can adjust adhesive properties betweencarbon fiber materials, graphite fiber materials and matrix in obtainedcomposite materials to solve the problem of brittle breaking of thecomposite materials due to too high adhesion, the problem of decreasingtensile strength in the fiber direction and the problem such as strengthproperties in the orthogonal direction of fiber are not developed due topoor adhesive properties of a resin though tensile strength in the fiberis high, so that well-balanced strength properties in both of fiber andorthogonal directions of the fiber are developed in the obtainedcomposite materials.

Thereafter, sizing treatment can also be performed for allowing theconverging to obtained carbon fiber materials. With regard to sizingagents, sizing agents having favorable compatibility with the resin canbe selected in accordance with the kinds of resin to be used.

With regard to sheetlike carbon products, carbon content is preferably80% by weight or more, more preferably 90% by weight or more. Thethickness thereof is preferably 5 mm or less, more preferably 2 mm orless and further more preferably 1 mm or less. The sheet thickness canproperly be selected in accordance with uses and may be a thickness ofapproximately 0.01 to 2 mm, such as the so-called film.

Sheetlike carbon products can be obtained by carbonizing theabove-mentioned sheetlike flame-resistant formed products. Specifically,the products can be obtained by treating in an inert atmosphere at atemperature of 300° C. or more and less than 2000° C. The maximumtemperature is 800° C. or more, 1000° C. or more and 1200° C. or more atthe lower limit in increasing order of preference, and usably 1800° C.or less at the upper limit.

Such sheetlike carbon products can also be made into sheetlike graphiteproducts by further heating in an inert atmosphere at a temperature of2000 to 3000° C.

A flame-resistant polymer-containing solution can also be applied as acoating of substrates. The coating of surfaces of glass substrates andmetal substrates provides flame, resistance, and the carbonization inthe same manner as the above-mentioned flame-resistant fiber alsoprovides carbon properties.

As described above, a manufacturing method of converting aflame-resistant polymer into carbon molded products throughflame-resistant formed products is described, and the step of obtainingflame-resistant formed products and the step of obtaining carbonproducts can each independently be performed or the steps can beperformed as one step directly connected with continuity.

Specifically, in the case of obtaining carbon fiber from aflame-resistant polymer through flame-resistant fiber, a flame-resistantpolymer-containing solution is spun into flame-resistant fiber tothereafter perform continuously up to carbonization without performingthe step of winding-up, and further perform one continuous processincluding the steps of surface treating and allowing sizing agents.

It is preferable to continuously manufacture in one process from aflame-resistant polymer to carbon products from the viewpoint of lowcosts.

EXAMPLES

Next, the disclosure is described more specifically by referring toexamples. In examples, each of physical property values and propertieswas measured by the following methods.

<Concentration of a Flame-Resistant Polymer-Containing Solution>

Approximately 15 mg of a flame-resistant polymer-containing solution wasprecisely weighed and heated at a rate of 20° C./minute from 25° C. upto 300° C. by using a thermogravimetric instrument (abbreviated to a TGinstrument), at which point of time the residual solid content wasmeasured as a flame-resistant polymer amount, and the flame-resistantpolymer amount was divided by a flame-resistant polymer-containingsolution amount to calculate a flame-resistant polymer concentration (%by weight) in percentages. TG-DTA2000SA manufactured by SeikoInstruments Inc. was used as the thermogravimetric instrument.

In the case of a flame-resistant polymer to be completely coagulated inwater, 5 g of a flame-resistant polymer-containing solution wasrepeatedly treated with 1 L of water heated to 90° C. for 30 minutesthree times to gather solid components only, which were dried at atemperature of 120° C. for 1 hour to separate a flame-resistant polymer.The weight thereof was measured, and the flame-resistant polymer amountwas divided by a flame-resistant polymer-containing solution amount tocalculate a flame-resistant polymer concentration (%) in percentages.

<Viscosity of a Flame-Resistant Polymer-Containing Solution>

The viscosity was measured on the conditions of a frequency of 0.1 Hzand an amplitude of 1° by using a plate-plate type rheometer ofSoliquidmeter (manufactured by Rheorogies Inc.). With regard to measuredtemperature, a value at a temperature of 50° C. was a central valuethrough measurements at temperatures of 25° C. to 150° C.

<NMR Measurement of a Flame-Resistant Polymer and a Flame-ResistantPolymer-Containing Solution>

A nuclear magnetic resonance spectrum of a flame-resistant polymer insolid was measured at an observed frequency of 75.2 MHz, an observedwidth of 30 kHz and a sample rotational speed of 10 kHz. CMX-300manufactured by Chemimagnetic Corporation was used as the nuclearmagnetic resonance apparatus.

A nuclear magnetic resonance spectrum of a flame-resistantpolymer-containing solution was measured at a measuring nuclearfrequency of 67.9 MHz, a spectrum width of 15015 kHz, a sample rotationnumber of 15 Hz by using the spectrum of solvent known at roomtemperature as internal standard. GX-270 manufactured by JEOL Ltd. wasused as the nuclear magnetic resonance apparatus.

<Evaluation Method of Flame Resistance>

A. Indefinite Polymer

Flame resistance of each sample was evaluated on the selected conditionsby a method in conformity to a fire resistance test method of thinmaterials (45° Meckel burner method) in JIS Z 2150 (1966). An indefinitepolymer was ground into particles of approximately 20 μm, which weremade into a disk having a diameter of 20 mm and a thickness of 1 mm byusing a pressure molding machine (a pressure of 10 MPa) to obtain asample. This disk was set in a test piece supporting frame inclined by45° and placed in a combustion test box, and heated with fire of aMeckel burner having a height of 160 mm and an inside diameter of 20 mmfor 10 seconds to evaluate flaming time and whether left as carbideafter combustion. Shorter flaming time, namely, time when the samplecontinued to burn with flame from the end of heating was more excellent,and the whole area including the carbide was measured while retainingthe shape of the sample; if 70% or more of the area before measuringremained, flame-resistant performance was evaluated as ‘excellent’. If40 to 70% or more thereof remained, flame-resistant performance wasdetermined as ‘favorable’, and if less than 40% thereof remained,flame-resistant performance was determined as ‘poor’.

B. Fiber

Fiber was made into a sample length of 30 cm with filaments of 1500pieces by doubling to measure flaming time and carbonized length byflame of the same Meckel burner in the same manner as evaluation of aflame-resistant polymer, and evaluate flame resistance from the values.The following were determined: excellent flame resistance (flaming timeof 10 seconds or less, carbonized length of 5 cm or less), favorableflame resistance (flaming time of 10 seconds or less, carbonized lengthof 10 cm or less), flame-resistant (flaming time of 10 seconds or less,carbonized length of 15 cm or less) or poor flame resistance (flamingtime of more than 10 seconds, carbonized length of more than 15 cm). Thenumber of measurement was n=5 and the most frequent state was regardedas flame resistance of the sample.

C. Sheet and Molded Products

Sheet and molded products were cut into a sample length of 30 cm and awidth of 1 cm, and evaluated in the same manner as flame-resistantfiber.

<Fiber Tensile Strength of Flame-Resistant Fiber and Carbon Fiber>

A tensile test was performed for either of the fibers in accordance withJIS L1015 (1981). Single fiber having a length of 25 mm was firmly fixedone by one to a slip of paper with smooth and glossy surface atintervals of 5 mm-width in a state such that both ends thereof were soloosely strained by an adhesive as to have a sample length ofapproximately 20 mm. The sample was attached to the grip of a singlefiber tensile tester to cut the slip of paper near the grip at the topand measure at a sample length of 20 mm and a tension speed of 20mm/minute. The number of measurement was n=50 and the average value wasregarded as tensile strength.

<Break Strength of Flame-Resistant Film and Carbon Film>

The tensile strength of films was measured at a temperature of 25° C.and 65% RH atmosphere by using a universal tensile tester in accordancewith a method prescribed in JIS K7127 (1999). Instron 5582 type materialtesting machine was used as the universal tensile tester, and a samplewas cut out to a size with a length of more than 100 mm and a strip ofpaper with a width of 10 mm. Initial tensile distance between chucks was100 mm and tension speed was 200 mm/minute. The number of measurementwas n=5 and the average value was regarded as break strength.

<Specific Gravity Measurement of Flame-Resistant Molded Products andCarbon Molded Products>

Automatic specific gravity-measuring equipment with an electronicbalance attached by immersion method was made oneself, and specifically,ethanol was used for flame-resistant molded products and dichlorobenzenewas used for carbon molded products, into which a sample was projectedand measured. The sample was previously wetted sufficiently in anotherbath by using ethanol or dichlorobenzene before being projected toperform air vent process.

<Crystal Size Measurement of Carbon Molded Products>

Carbon fiber was cut into a length of 4 cm, fixed by using a metal moldand an alcoholic solution of corosion and made into a square pillar,which was regarded as a measurement sample. The measurement wasperformed with CuKcα (Ni filter) as an X-ray source and an output of 40kV and 20 mA by using a wide-angle X-ray diffractometer manufactured byRigaku Denki Corporation.

Molded products except fiber were similarly cut into a desired size tothereafter make a sample and measure crystal size.

<Nitrogen Content of Carbon Molded Products>

A sample was subjected to oxidative decomposition and measured by usinga CHN coder MT-3 type apparatus manufactured by Yanagimoto Ltd. on theconditions of a sample cracking furnace at 950° C., an oxidation furnaceat 850° C. and a reducing furnace at 550° C.

Example 1

20 parts by weight of particulates of polyacrylonitrile-based copolymerobtained from 99.5 mol % of acrylonitrile and 0.5 mol % of itaconic acidby aqueous slurry polymerization method, and 74 parts by weight ofmonoethanolamine were weighed, projected into a flask, stirred andheated to a temperature of 160° C. The contents were discolored intoorange through the gradual progress of cyclization reaction and otherchemical reactions. The contents were dissolved in approximately 20minutes and further stirred for 10 minutes.

Thereafter, 6 parts by weight of ortho-nitrotoluene was added to thesolution, which was discolored from blackish brown into black byoxidation reaction, directly stirred at a temperature of 160° C. for 30minutes, and cooled after finishing the reaction to obtain aflame-resistant polymer-containing solution. The flame-resistantpolymer-containing solution was treated at a temperature of 300° C. toremove solvent and volatile component, and obtain a flame-resistantpolymer. When flame resistance of this flame-resistant polymer wasevaluated with a disk sample in accordance with the above-mentionedmethod, it was found that flaming time was as short as 8 seconds and 80%of the whole area remained in the shape of including the carbide, sothat flame resistance was excellent.

The viscosity of the flame-resistant polymer-containing solution was1000 Pa·s at a temperature of 25° C. and 150 Pa·s at a temperature of50° C.

The flame-resistant polymer-containing solution was analyzed by 13C-NMRand then found to be a solution containing 4% by weight of o-toluisinebesides monoethanolamine as solvent. A peak derived from chemicalstructure of the flame-resistant polymer, which was not recognized inpolyacrylonitrile as a precursor polymer and solvents, existeddefinitely at 160 to 180 ppm.

The concentration of the flame-resistant polymer in the flame-resistantpolymer-containing solution was 40% by weight measured by theabove-mentioned method. That is, polyacrylonitrile polymer concentrationof 20% by weight became flame-resistant polymer concentration of 40% byweight by denaturation with monoethanolamine as solvent, resulting in anincrease to twice the amount of a precursor polymer.

Example 2

The flame-resistant polymer-containing solution of Example 1 wasfibrillated by a dry spinning apparatus shown in FIG. 1. Specifically,the flame-resistant polymer-containing solution was discharged through aflame-resistant polymer flow path 1 from a mouthpiece having three holeswith a diameter of 0.15 mm at a spinning head 2 to a spinning chimney 3retained in an atmosphere of 300° C. by heated nitrogen to vaporizesolvent. The spinning chimney 3 had a heated nitrogen inlet 4 and aheated nitrogen outlet, and the heated nitrogen flew in and out throughthese inlet and outlet. The obtained fibrous flame-resistant moldedproduct 6 was once wound up on a wind-up roller 7 at a roller rate of100 in/minute, which wind-up roller was detached to remove the remainingvolatile component by further heat-treating in an oven at a temperatureof 300° C. for 5 minutes, and obtain flame-resistant fiber. In FIG. 1,the spinning chimney 3 is shown with partial cutoff for the purpose ofdescribing the inside.

With regard to the obtained flame-resistant fiber, the degree offineness of single fiber was 2.0 dtex, the strength was 2.0 g/dtex andthe ductility was 20%, and flame resistance was evaluated with singlefiber, which was then found to be so red hot without burning as to haveas excellent flame resistance as a carbonized length of 2 cm.

In addition, the flame-resistant fiber obtained from the flame-resistantpolymer was preliminarily carbonized in a nitrogen atmosphere at atemperature of 300 to 800° C., and subsequently carbonized in a nitrogenatmosphere at a temperature of 1400° C. The strength of the obtainedcarbon fiber was 1600 MPa and the modulus of elasticity was 160 GPa.

Example 3

The flame-resistant polymer-containing solution of Example 1 was formedinto a film by cast film forming method. Specific processes are asfollows. First, the flame-resistant polymer-containing solution was caston a glass plate with uniform thickness. The glass plate was dried in aconstant-temperature dryer at a temperature of 100° C. for 5 minutes toonce peel the obtained polymer off the glass plate. Thereafter, theglass plate was fixed to a metallic flask and treated in air atmosphereat a temperature of 300° C. for 5 minutes to thereby remove excessivesolvent and volatile component, and obtain a flame-resistant film.

The final thickness of this flame-resistant film was found to measure0.03 mm by a contact-type thickness meter. The break strength of theobtained flame-resistant film was 180 MPa and the ductility was 18%.

When flame resistance of this flame-resistant film was evaluated by theabove-mentioned method, it was found that combustion did not continuedespite slight ignition once and the shape was retained with acarbonized length of 2 cm after fire went out, so that flame resistancewas excellent.

In addition, this flame-resistant film was preliminarily carbonized innitrogen atmosphere at a temperature of 300 to 800° C., and subsequentlycarbonized in a nitrogen atmosphere at a temperature of 1400° C. tothereby obtain a carbon film. The break strength of the obtained carbonfilm was 1200 MPa and the ductility was 1.5%.

Example 4

A surface of a stainless-steel plate was coated with the flame-resistantpolymer-containing solution of Example 1, and put in an oven at atemperature of 100° C. to remove solvent and volatile component for 5minutes, and further remove the remaining solvent and volatile componentat a temperature of 300° C. for 5 minutes and fix a surface coating filmhaving a thickness of 10 μm. Flame resistance of this molded product wasevaluated by the same method as Example 3, and then found to be soexcellent as to have no ignition and a carbonized length of 2 cm.

In addition, this molded product was preliminarily carbonized in aninert atmosphere at a temperature of 300 to 800° C., and subsequentlycarbonized in an inert atmosphere at a temperature of 900° C. to obtaina stainless-steel plate having a surface coating film consistingessentially of carbon.

Example 5

Copolymer fiber (the degree of fineness of single fiber was 0.9 dtex andthe number of filaments was 3000) obtained from 99.5 mol % ofacrylonitrile and 0.5 mol % of itaconic acid was subjected to airoxidation at a temperature of 240° C. for 100 minutes. Flame resistanceof the obtained fiber was evaluated by the same method as Example 3,which fiber was then found to have so excellent flame resistance as tohave no ignition and a carbonized length of 2 cm. 20 parts by weight ofthe flame-resistant fiber and 80 parts by weight of triethylenetetramineas solvent thereof were projected into a flask and heated to refluxwhile stirred for 2 hours to obtain a flame-resistant polymer-containingsolution.

A very small amount of insoluble component was removed by hot filtrationto thereafter manufacture a flame-resistant film by the same method asExample 3. Flame resistance of the obtained flame-resistant film was asexcellent as a carbonized length of 3 cm.

Example 6

100 parts by weight of acrylonitrile, 0.6 parts by weight of itaconicacid, 371 parts by weight of dimethyl sulfoxide, 0.4 parts by weight ofazobisisobutyronitrile and 1 part by weight of octylmercaptan werecharged into a reaction vessel and nitrogen-substituted, and thereafterheated and polymerized at 65° C. for 5 hours and at 75° C. for 7 hoursto prepare solution containing polyacrylonitrile copolymer (PAN)comprising 99.5 mol % of acrylonitrile having dimethylsulfoxide (DMSO)as solvent thereof and 0.5 mol % of itaconic acid. The whole system wasdecompressed to 30 hPa by exhaust with the use of a pump for removingmonomer, and thereafter warmed up to 160° C., to which DMSO andmonoethanolamine (MEA) were added and reacted in a uniform state for 60minutes. Ortho-nitrotoluene (ONT) was further added and reacted at 160°C. for 120 minutes to obtain a black flame-resistant polymer-containingsolution. The charge weight ratio on this occasion wasPAN/DMSO/MEA/ONT=12/77/8/3.

The viscosity of the flame-resistant polymer-containing solutionobtained by cooling was 300 Pa·s at a temperature of 25° C. and 100 Pa·sat a temperature of 50° C.

The flame-resistant polymer was projected into warm water to separatecoagulated polymer by filtration, which polymer was dried at atemperature of 120° C. to isolate the flame-resistant polymer. 13C-NMRanalysis was performed in a solid state by DDMAS method and CPMASmethod. A-1 of FIG. 2 is the spectrum by DDMAS method and A-2 is thespectrum by CPMAS method. B of FIG. 2 is the spectrum of theflame-resistant fiber with no amine denaturation obtained in Example 5.A peak derived from the flame-resistant polymer, which was notrecognized in polyacrylonitrile as a precursor polymer, existed atchemical shift of 160 to 180 ppm in A-1 and A-2 of FIG. 2, and thespectrum by CPMAS method for measuring a portion of low molecularmobility was similar to that of the flame-resistant fiber with no aminedenaturation. In DDMAS method for measuring a portion of high molecularmobility, a chemical bond peak of MEA used as an amine denaturant wasrecognized particularly obviously at 40 to 50 ppm and 58 to 68 ppm, sothat it was found that MEA chemically modifies the flame-resistantpolymer, which was taken in polymer backbone.

The concentration of the flame-resistant polymer in the flame-resistantpolymer-containing solution was 18.5% by weight measured by theabove-mentioned method. That is, polyacrylonitrile polymer concentrationof 12% by weight became flame-resistant polymer concentration of 18.5%by weight by denaturation with monoethanolamine and the like, resultingin an increase to 1.54 times the amount of a precursor polymer.

When flame resistance of the flame-resistant polymer was evaluated inthe same manner as Example 1, it was found that flaming time was asshort as 8 seconds and a shape of nearly 100%-disk was retained, so thatflame resistance was excellent.

Example 7

The flame-resistant polymer-containing solution of Example 6 wasfibrillated by a wet spinning apparatus. Specifically, theflame-resistant polymer-containing solution was discharged from amouthpiece having 100 holes with a diameter of 0.08 mm into a water bathat a temperature of 20° C. to substitute solvents with water, andthereafter the solution was passed through a roller at a roller rate of10 m/minute and further washed to allow amine silicone oil solutionthereto, and thereafter the solution was dried by heating with the useof a heated roll at a temperature of 180° C. and further drawn by 1.8times at a temperature of 300° C. and simultaneously heat-treated toobtain flame-resistant fiber.

With regard to the obtained flame-resistant fiber, the degree offineness of single fiber was 3.0 dtex, the strength was 2.5 g/dtex andthe ductility was 18%, and flame resistance thereof was evaluated, whichfiber was then found to be so red hot without burning as to have asexcellent flame resistance as a carbonized length of 1 cm.

In addition, the flame-resistant fiber obtained from the flame-resistantpolymer was preliminarily carbonized in nitrogen atmosphere at atemperature of 300 to 800° C., and subsequently carbonized in nitrogenatmosphere at a temperature of 1400° C. The strength of the obtainedcarbon fiber was 1800 MPa, the modulus of elasticity was 200 GPa and thespecific gravity was 1.54.

The obtained carbon fiber was measured by wide-angle X-rays and thenfound to have a crystal size of 25 angstroms and as much N content as 8%calculated from elemental analysis, which satisfied[N≧0.04(Lc−30)^2+0.5].

Example 8

100 parts by weight of acrylonitrile, 371 parts by weight ofdimethylsulfoxide, 0.4 parts by weight of azobisisobutyronitrile and 1.6parts by weight of octylmercaptan were charged into a reaction vesseland nitrogen-substituted, and thereafter heated and polymerized at 65°C. for 5 hours and at 75° C. for 7 hours to prepare solution containingpolyacrylonitrile (homo-PAN) comprising substantially 100% ofacrylonitrile having dimethylsulfoxide (DMSO) as solvent thereof, whichsolution was subjected to removing monomer. DMSO and ONT were furtheradded and warmed up to 150° C., to which monoethanolamine (MEA) wereadded and uniformly reacted for 60 minutes to obtain a flame-resistantpolymer-containing solution. The charge weight ratio on this occasionwas homo-PAN/DMSO/MEA/ONT=10/76/8/6.

The viscosity of the flame-resistant polymer-containing solutionobtained by cooling was 50 Pa·s at a temperature of 25° C. and 30 Pa·sat a temperature of 50° C.

The flame-resistant polymer was projected into warm water to separatecoagulated polymer by filtration, which polymer was dried at atemperature of 120° C. to isolate the flame-resistant polymer. Whenanalyzed by 13C-NMR, a peak derived from the flame-resistant polymer,which was not recognized in polyacrylonitrile as a precursor polymer,solvents and denaturants, existed definitely at 160 to 180 ppm.

The concentration of the flame-resistant polymer in the flame-resistantpolymer-containing solution was 13% by weight measured by theabove-mentioned method. That is, polyacrylonitrile polymer concentrationof 10% by weight became flame-resistant polymer concentration of 13% byweight by denaturation with monoethanolamine, resulting in an increaseto 1.3 times the amount of a precursor polymer.

When flame resistance of the flame-resistant polymer was evaluated inthe same manner as Example 1, it was found that flaming time was asshort as 8 seconds and a shape of nearly 100%-disk was retained, so thatflame resistance was excellent.

Example 9

The flame-resistant polymer-containing solution of Example 8 wasfibrillated by a wet spinning apparatus. Specifically, theflame-resistant polymer-containing solution was discharged from amouthpiece having 100 holes with a diameter of 0.08 mm into a water bathaccommodating 20% by weight of DMSO at a temperature of 20° C. tosubstitute solvents with water, and thereafter the solution was passedthrough a roller at a roller rate of 10 in/minute, and further washedand dried by heating with the use of a heated roll at a temperature of180° C., and further drawn by 1.5 times at a temperature of 300° C. andsimultaneously heat-treated to obtain flame-resistant fiber.

With regard to the obtained flame-resistant fiber, the degree offineness of single fiber was 1.6 dtex, the strength was 2.8 g/dtex andthe ductility was 17%, and flame resistance was evaluated with singlefiber, which was then found to be so red hot without burning as to haveas excellent flame resistance as a carbonized length of 1 cm.

In addition, the flame-resistant fiber obtained from the flame-resistantpolymer was preliminarily carbonized in a nitrogen atmosphere at atemperature of 300 to 800° C., and subsequently carbonized in nitrogenatmosphere at a temperature of 1400° C. The strength of the obtainedcarbon fiber was 2000 MPa, the modulus of elasticity was 210 GPa and thespecific gravity was 1.65.

The crystal size of the obtained carbon fiber was 24 angstroms and thenitrogen content was 7.8% by weight, leading to the retainment of highcrystal size and nitrogen content, which satisfied[N≧0.04(Lc−30)^2+0.5].

Comparative Example 1

A flame-resistant polymer-containing solution attempted to be obtainedin the same manner as Example 5 except for modifying the solvent tonitric acid. Though the temperature was modified to a range of 50 to300° C., the flame-resistant fiber could not sufficiently be dissolved,so that a flame-resistant polymer-containing solution could not beobtained.

INDUSTRIAL APPLICABILITY

A flame-resistant polymer can widely be utilized as fire-resistant fiberproducts by forming into flame-resistant fiber. Flame-resistant fiber iscarbonized and made into carbon fiber, which can widely be utilized asreinforced fiber of composite materials.

A flame-resistant polymer-containing solution can be used for all useswith flame resistance required by reason of being capable of forminginto optional shapes such as sheets and molded products in addition tofiber. Flame-resistant products are easily made into carbon products,which are also useful for electrical parts and electronic parts.

1. A carbon molded product comprising a part or the whole thereofcomposed of a carbon component obtained by carbonizing a flame-resistantpolymer that is soluble in a polar organic solvent and denatured with anamine compound.
 2. The carbon molded product according to claim 1, whichis fibrous.
 3. The carbon molded product according to claim 1, which issheet and has a thickness of 5 mm or less.
 4. The carbon molded productaccording to claim 1, wherein a crystal size Lc measured by wide-angleX-ray is 30 angstroms or less, and Lc and a nitrogen content N (% byweight) satisfy (N≧0.04(Lc−30)^2+0.5).
 5. The carbon molded productaccording to claim 2, wherein a crystal size Lc measured by wide-angleX-ray is 30 angstroms or less, and Lc and a nitrogen content N (% byweight) satisfy (N≧0.04(Lc−30)^2+0.5).
 6. The carbon molded productaccording to claim 3, wherein a crystal size Lc measured by wide-angleX-ray is 30 angstroms or less, and Lc and a nitrogen content N (% byweight) satisfy (N>0.04(Lc−30)^2+0.5).
 7. A method of manufacturing acarbon molded product comprising carbonizing a flame-resistant formedproduct which comprises a part or the whole thereof composed of aflame-resistant polymer denatured with an amine compound.